Based on a quick look at Wikipedia for GSM, it sounds like some efforts have been made towards breaking the encryption: https://en.m.wikipedia.org/wiki/GSM http

Based on a quick look at Wikipedia for GSM, it sounds like some efforts have been made towards breaking the encryption: https://en.m.wikipedia.org/wiki/GSM https://en.m.wikipedia.org/wiki/GSM I'd be willing to bet that national governments have done even more work on that problem.